<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script src="js/jquery-3.4.1.min.js"></script>
    <style>
        .d{
            background: yellow;
            width: 100px;
            height: 100px;
        }
    </style>
</head>
<body>
    <div></div>
    <input type="text">
    <button>提交</button>
    <script>
        $(function(){
            $('div').addClass('d')
            alert($('div').hasClass('d'))
            //判断有没有这个属性

            // alert($('div').css("height"))
            //获取样式的值

            $('div').html("<p>0000000</p>")

            $('button').click(function(){
                let s = $('input').val()
                alert(s)
            })
        })
    </script>
</body>
</html>